openssl: Fix wincrypt symbols conflict with BoringSSL

openssl: Fix wincrypt symbols conflict with BoringSSL

OpenSSL undefines the conflicting symbols but BoringSSL does not so we
must do it ourselves.

Reported-by: Samuel Tranchet
Assisted-by: Javier Blazquez
Ref: https://bugs.chromium.org/p/boringssl/issues/detail?id=371
Ref: https://github.com/openssl/openssl/blob/OpenSSL_1_1_1g/include/openssl/ossl_typ.h#L66-L73

Fixes https://github.com/curl/curl/issues/5669
Closes https://github.com/curl/curl/pull/5857